1 //===-- LoopAligner.cpp - Loop aligner pass. ------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the pass that align loop headers to target specific
11 // alignment boundary.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "loopalign"
16 #include "llvm/CodeGen/MachineLoopInfo.h"
17 #include "llvm/CodeGen/MachineFunctionPass.h"
18 #include "llvm/CodeGen/Passes.h"
19 #include "llvm/Target/TargetLowering.h"
20 #include "llvm/Target/TargetMachine.h"
21 #include "llvm/Support/Compiler.h"
22 #include "llvm/Support/Debug.h"
26 class LoopAligner : public MachineFunctionPass {
27 const TargetLowering *TLI;
31 LoopAligner() : MachineFunctionPass((intptr_t)&ID) {}
33 virtual bool runOnMachineFunction(MachineFunction &MF);
34 virtual const char *getPassName() const { return "Loop aligner"; }
36 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
37 AU.addRequired<MachineLoopInfo>();
38 AU.addPreserved<MachineLoopInfo>();
39 MachineFunctionPass::getAnalysisUsage(AU);
43 char LoopAligner::ID = 0;
44 } // end anonymous namespace
46 FunctionPass *llvm::createLoopAlignerPass() { return new LoopAligner(); }
48 bool LoopAligner::runOnMachineFunction(MachineFunction &MF) {
49 const MachineLoopInfo *MLI = &getAnalysis<MachineLoopInfo>();
51 if (MLI->begin() == MLI->end())
52 return false; // No loops.
54 unsigned Align = MF.getTarget().getTargetLowering()->getPrefLoopAlignment();
56 return false; // Don't care about loop alignment.
58 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
59 MachineBasicBlock *MBB = I;
60 if (MLI->isLoopHeader(MBB))
61 MBB->setAlignment(Align);